The present invention relates to driving tools and more particularly to a driving bit linking device in a box wrench which is provided to engage and/or disengage different types of driving bit within the box wrench which is operated manually or by power.
The using a box wrench to actuate a driving bit for fastening or unfastening a working piece such as a screw is usually used by carpenter, electrician and blacksmith. The issue coming up is how to improve the structure of the linking device in the box wrench in order to facilitate a readily engagement or disengagement of the driving bit with the wrench.
FIGS. 1 and 2 show a prior art linking device in a box wrench which comprises a box wrench 10, a conical spring 12 embedded in the bottom of the wrench 10 and restricted by an annular ring 13, an annular ring 15 on an outer periphery, a slant slot 11 in a periphery above the annular ring 15, a compressed spring 18 wrapped on the outer periphery stopped on the top of the annular ring 15 including a U-shaped checking rod 181 horizontally attached on the top thereof, a cap 17 sleeved on the outer periphery of the wrench 10 and restrained by a retaining ring 14 which is secured into an annular groove 141 abutting the upper rim of the wrench 10, an annular groove 16 under the annular ring 15 for engaging therein another retaining ring 161 for restraining the annular ring 15 from moving downward, under the wrench 10, there is a cylindrical rod 108 having crossed grooves 109 through entire outer periphery for guiding a sleeve 103 which has a plurality of spaced apart teeth 104 around outer periphery abutting lower rim and several convex on inner periphery engaged with the crossed grooves 109, an annular cap 105 closed the top of a hollow cylindrical body 106 which connects to a handle 107 in which is a checking and rotation control mechanism and a spring. When a driving bit 101 is under pressure, the crossed grooves 109 follow the convex to rotate the cylindrical rod 108 as to actuate the driving bit 101 to fasten a working object. The driving bit 101 is able to insertion into the wrench and secured by the checking rod 108 without breaking off. When press the cap 17 downward to force the checking rod disengaged with the concaves 102 so as to permit the driving bit 101 to remove out of the wrench 10 (as shown in FIG. 3).
The driving bit has different types such as the C type bit which has concaves in outer periphery and E type bit which has an annular groove on outer periphery. This structure of the wrench 10 only fits to the C type bit and could not secure the E type bit, especially the double tip bit which would damage the spring in the wrench for instance, to entangled with the spring or to cause the spring becoming deformed. So that this type of box wrench is limited in use.
Another prior art box wrench (as shown in FIGS. 4 and 5) comprises a box wrench 20 and a cap 27. The box wrench 20 has a conical spring 22 in the bottom and restrained by an annular ring 23, a slant through hole 21 in a middle periphery, a compressed spring 28 wrapped on the lower outer periphery stopped on the top of an annular ring 25 and including a U-shaped checking rod 29 on the top and inserted into the slant through hole 21 and a retaining ring 241 engaged into an annular groove 241 abutting the upper ring of the wrench 20 for preventing the cap 27 from breaking off, a driving bit 201 inserted into the wrench 20 having an annular groove 202 in lower periphery arrested by the U-shaped checking rod 29. When press the cap 27 downward, the checking rod 29 is forced to move downward to so as to disengaged with the annular groove 202 to permit the driving bit 20 removing from the wrench 20. This type of box wrench 20 also not fits to the double tips driving bit, because it also damages the spring 22 or causes the spring 22 deformed (as shown in FIG. 6). Besides, it not fits to the concaved driving bit. Therefore, the utility of this type of box wrench 20 is also limited.